1. Field of the Invention
The present invention relates to a semiconductor device provided with a field effect transistor having a metal insulator semiconductor structure (MISFET) and using an FT (Filled Tetrahedral) semiconductor as a channel.
2. Description of the Related Art
Generally, there is an increasing demand for electronic elements to be used for configuring various information processing systems with a high processing speed as the amount of information to be processed has increased remarkably in recent years. Thus, there is also an increasing demand for high performance and high function CMOS electronic elements. For example, JP-A2001-160594 (KOKAI) discloses the use of high mobility channel material that utilizes strained Si, strained SiGe or the like for the purpose of realizing a high mobility element. Such strained Si can increase the mobility of both electrons and holes if compared with unstrained Si as tensile strain is generated in intra-planar directions and the band structure is changed due to the influence of the strain. Thus, CMOS formed by using a MOSFET having such a strained Si channel can operate at a speed higher than a conventional Si—CMOS of the same size by about 60%.
Strained SiGe has compression strain in intra-planar directions of the substrate. The band structure is changed due to the influence of the compression strain to increase the hole mobility if compared with unstrained Si. Note, however, that the electron mobility is not increased significantly if compared with the increase of the hole mobility. Thus, it is expected that a CMOS that is formed by using a MOSFET having a strained SiGe channel that shows a high Ge composition will operate faster than a strained Si—CMOS of the same size.
However, any of the above-described techniques faces difficulties in terms of process of introducing strain, process of controlling strain, minimization of interface defects, process complexity and so on. Additionally, if strained SiGe is used, the operation speed may be doubled at most. Therefore, the requirements for realizing high performance and high function CMOS electronic elements in the future have not been met satisfactorily. Phys. Rev. Lett. 52675 (1984) proposes an FT (filled tetrahedral) semiconductor structure that is realized by using rare gas. However, there has not been any instance where such a structure is applied to LSI because it is unstable in the LSI thermal process. Therefore, no study has been reported on electric characteristics of FT semiconductors.
Common knowledge technology including JP-A2001-160594 (KOKAI) and Phys. Rev. Lett. 52675 (1984) as listed above cannot satisfactorily modulate the band structure of silicon and hence cannot form a channel showing a sufficient degree of mobility.